I just want to show you the way to make quite nice random looking grass.I hope that it will be useful to you.

Firstly I made one plane(ground), then I scattered another one(grass object - 4polys) over the ground with scatter tool. Which I set 8000 duplicates.
It is enough for this situation, but the number of duplicates depents on situation, I just want to show you my way.Here is what I have done so far.(display in scatter modifier is set to 10%)

Than I applied the first vol.select modifier to our scattered grass. I made a noise map for this modifier and assigned to it. All settings are on the next picture.(notice that in scatter modifier is now set display to 100%)

Then I applied another vol.select modifier. I made other noise map with smaller size(you can make your own maps - not just noise - but noise is easy tweakable for this situation) for this one is important to check subtract in this modifier. Look at following picture.

Then I applied the deletemesh modifier to delete polys that were selected by vol.select modifiers to have non-regular looking grass like on the picture.

Now you can play with size of noisemaps in mat.ed.(to obtain effect you want) and see the result directly in the viewport. Than I played around within edit mesh modifier(applied on the top of modifier stack) with soft selection to lower some vertices - especialy in those areas with fewer polys. Finaly I applied a texture map and opacity map (I painted both in ps) to scettered grass and other map to ground.You should make your own maps in ps for vol.select to get what you want and can also scatter different types of grass for a very nice looking grass.You should have more vol,select modifiers etc. I hope this will help you. And this is the result that I achieved by this metod.